In recent years, the market of equipment dealing with still-images such as digital still cameras and printers has been making steady expansion. So far, such devices have been used in the environment where personal computers exist. Recently, the user's need for easy handling of these devices in the non-PC environment is now increasingly growing.
In a conventional data transfer technology, when transceiving data of the type which does not require real-time processing (e.g., still-image data and document data) between two devices, generally one of the devices issues a command to the other for the exchange of the data therebetween.
FIG. 17 is a block diagram illustrating a first example of a still-image data system according to a conventional data transfer method. FIG. 17 shows a digital still camera 100 serving as an image input device and a printer 101 serving as an image output device. The user operates an operation button of the digital still camera 100 to select an internally-stored image and issues an instruction so that the selected image enters the printer 101. Then, the digital still camera 100 issues a data reception command 102 to the printer 101, thereby to bring the printer 101 into its data receivable state. This is followed by a transfer of data 103.
Referring next to FIG. 18, there is shown a second example of the still-image data system according to the conventional data transfer method. With reference to FIG. 18, an example case will be described in which the user operates an operation panel of the printer 101 so that a specified image is taken from the digital still camera 100. The user issues an instruction by operating an operation button of the printer 101 so that image data stored in the digital still camera 100 is to be taken therefrom. Then, the printer 101 issues a data transmission command 104 to the digital still camera 100. Upon receipt of the data transmission command 104, the digital still camera 100 carries out a process of transferring the data 103 to the printer 101.
Further, for the realization of networking of a plurality of terminal devices including the digital still camera 100 and the printer 101, a conventional example configuration shown in FIG. 19 has been known in the art. FIG. 19 is a diagram illustrating a third example of the still-image data system according to the conventional data transfer method. Referring to FIG. 19, an example case will be described in which a third device, such as a personal computer and digital TV set-top box, issues an instruction so that image data is transferred from the digital still camera 100 to the printer 101.
FIG. 19 shows a personal computer indicated by the reference numeral 105. In the first place, the personal computer 105 issues the data input command 104 to the digital still camera 100, so that the data 103 is temporarily stored in the personal computer 105. Next, the personal computer 105 issues the data output command 102 to the printer 101, and performs a process of transmitting to the printer 101 the stored data 103 previously received from the digital still camera 100. The same data (i.e., the data 103) is first transferred from the digital still camera 100 to the personal computer 105 and then transferred from the personal computer 105 to the printer 101. In other words, the transfer of the data 103 requires two process steps. Moreover, it is required to transfer the same data twice, resulting in increasing the processing time. In addition, there is produced the requirement that storage space for storing the data 103 be secured in the personal computer 105. Accordingly, the system becomes poor in operation efficiency.
Therefore, as a data transfer method capable of improving the efficiency of the aforesaid commonly-employed data transfer method, the COPY COMMAND (see Small Computer System Interface (SCSI), ANSI X3. 131-1986) has been proposed in the art.
FIG. 20 provides a description of the operation of a still-image data system employing a COPY COMMAND data transfer method.
FIG. 20 shows a COPY command indicated 106 by which the personal computer 105 directs the digital still camera 100 to transmit image data, a first error notification 107 by which an error occurring in the printer 101 is transmitted to the digital still camera 100, and a second error notification 108 by which the error occurrence in the printer 101 is transferred from the digital still camera 100 to the personal computer 105.
In the first place, the personal computer 105 issues to the digital still camera 100 the COPY command 106, the COPY command 106 containing therein an indication of TRANSFER IMAGE DATA TO PRINTER 101. The COPY command 106 contains the contents of the data reception command 102 (see FIG. 17), together with an identifier (SCSI ID) of the printer 101.
Upon receipt of the COPY command 106, the digital still camera 100 interprets the identifier of the printer 101 and the contents of the data reception command 102 which are contained in the received COPY command 106 and issues the data reception command 102 to the printer 101. This is followed by transmission of the data 103 to the printer 101 from the digital still camera 100.
Therefore, according to the improved data transfer method shown in FIG. 20, the digital still camera 100 can send the data 103 directly to the printer 101 when the third control device (i.e., the personal computer 105) issues a command indicative of a data transfer. Accordingly, in comparison with the configuration of FIG. 19, the method of FIG. 20 certainly provides improved processing efficiencies.
In the conventional configuration shown in FIG. 20, if an error (such as out of paper or paper jam) occurs in the printer 101 during data transfer therefore making it impossible for the printer 101 to continue data reception any more, the printer 101 will notify the digital still camera 100 of a state of the error by the issuing of the first error communication 107 of FIG. 20. Upon receipt of the error state notification from the printer 101, the digital still camera 100 notifies the personal computer 105 of such an error occurrence in the printer 101 by the issuing of the second error communication 108. Accordingly, it is not until the reception of the second error communication 108 that the personal computer 105 becomes aware of the fact that the error has occurred in the printer 101.
To sum up, in an error situation as described above, the personal computer 105 is not informed of occurrence of the error directly from a device in which the error has taken place. In other words, it is necessary to propagate an error notification within the system, which is inefficient. In addition to such a drawback, there is produced another problem that the personal computer 105 has to determine, upon receipt of an error notification from digital still camera 100, whether the notified error has occurred in the digital still camera 100 or in the printer 101. The contents of the processing become complicated accordingly.
Further, the COPY command 106 differs from the data reception and transmission commands 102 and 104 previously described by reference to FIG. 19 and other figures in that the COPY command 106 is used only in the presence of a third control device as shown in FIG. 20, so that, in order to cope with various device connection environments or system configurations, it has conventionally been necessary for each device to support these two commands which differ from each other in processing type.
As described above, for the case of a system which transfers still-image data by employing a data transfer method as shown in FIGS. 17 and 18 (that is, the transceiving of data is carried out by one device issuing a command to the other device) in a network structure in which a third control device (e.g., the personal computer 105 of FIG. 19) is connected in the middle, there is the problem that the system becomes poor in operation efficiency and requires a more-than-necessary processing time, as described above.
Further, even when employing the improved data transfer method shown in FIG. 20, processing at error occurrence time is inefficient as previously described. In addition, it is required to support both a command of a first type used in a one-to-one connection and a command of a second type different from the first type, in other words two different types of commands must be supported. As a result, the capacity of software that is installed on equipment grows unnecessarily large and the software becomes complicated.